1. Field of the Invention
The present invention relates to a fuel injection control apparatus, and more particularly to a fuel injection control apparatus for determining an injection quantity of fuel so as to be capable of increasing the drivability upon acceleration in response to a subtle throttle action.
2. Description of Background Art
A fuel injection control apparatus is known for performing fuel injection in synchronism with the rotation of an engine and also performing asynchronous fuel injection to make up for an insufficient amount of fuel upon quick acceleration when no sufficient fuel supply is achieved by synchronous fuel injection. For example, Japanese laid-open patent publication No. 10-259749 discloses a fuel injection control apparatus which is capable of normalizing an injection quantity and an injection timing of asynchronous fuel injection depending on the acceleration pattern. The disclosed fuel injection control apparatus detects an acceleration pattern based on a change in the throttle opening, and particularly calculates the difference between throttle openings read at certain time intervals and determines the product of such differences. The product of differences well reflects an acceleration pattern to calculate an appropriate acceleration corrective quantity.
The above apparatus for calculating an acceleration corrective quantity depending on a rate of change of the throttle opening suffers the following problems: In order to calculate an accurate rate of change of the throttle opening, it is necessary that a certain large change in the throttle opening be produced. Unlike four-wheeled motor vehicles whose accelerator pedal is operated by an individual""s foot, two-wheeled motor vehicles whose throttle valve is opened and closed by hand needs a subtle throttle action. Fuel injection control for two-wheeled motor vehicles requires an acceleration corrective quantity to reflect a change in the throttle opening which is caused by a subtle throttle action. However, the above apparatus fails to provide a sufficient level of accuracy for fuel injection control under subtle throttle actions.
The present invention has been made to solve the above objects. It is an object of the present invention to provide a fuel injection control apparatus which is capable of increasing the drivability by way of accurate acceleration correction for subtle throttle actions.
To achieve the above object, there is provided in accordance with a first feature of the present invention a fuel injection control apparatus having rate-of-change calculating means for calculating two rates of change of a throttle opening which have been converted for comparison with each other, based on a detected change of the throttle opening prior to two different unit times with respect to a predetermined crankshaft rotational angle which is a timing for calculating a rate of change of the throttle opening, and acceleration corrective quantity calculating means for calculating an acceleration corrective quantity of an amount of injected fuel corresponding to a larger one of the two rates of change of the throttle opening.
According to the first feature, since rates of change of the throttle opening are detected in two different unit times, an ability to detect an abrupt throttle action is increased by a rate of change of the throttle opening in shorter unit times, allowing throttle actions to be detected stably due to a rate of change of the throttle opening in longer unit times, unlike the detection of a rate of change of the throttle opening in one unit time.
According to a second feature of the present invention, the rate-of-change calculating means is arranged to calculate two rates of change of the throttle opening which have been converted for comparison with each other, based on a change of the throttle opening prior to two different crankshaft rotational angles with respect to a predetermined crankshaft rotational angle. According to the second feature, it is possible to detect rates of change of the throttle opening in two different unit times from a detected crankshaft rotational angle without the need for timer means.
According to a third feature of the present invention, the basic fuel injection quantity is calculated per a predetermined calculation timing, and the fuel injection control apparatus has maximum value calculating means for calculating a maximum value of rates of change of the throttle opening which have been calculated by the rate-of-change calculating means between a preceding calculation timing and a present calculation timing, per the calculation timing, the acceleration corrective quantity calculating means being arranged to calculate an acceleration corrective quantity of the amount of injected fuel corresponding to the maximum value. According to the third feature, the accuracy of detection can be increased by performing acceleration correction corresponding to a maximum value of rates of change of the throttle opening between calculation timings.
According to a fourth feature of the present invention, the fuel injection control apparatus includes point calculating means for calculating a point corresponding to the maximum value, and adding means for calculating a total value of points per a predetermined number of times, and the acceleration corrective quantity calculating means calculates an acceleration corrective quantity only if the total value is greater than a reference value. According to the fourth feature, even when the rate of change of the throttle opening is small, if a point is calculated in each cycle, then since the total value is large, a stable accelerated state is detected, and an acceleration corrective quantity is calculated according to the maximum value of the latest rate of change of the throttle opening at that time. If a point is not calculated in each cycle, e.g., if the throttle opening changes due to noise or a reading tolerance, then since the total value is small, no acceleration corrective quantity is calculated.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.